This invention relates to monitoring fluid flow in fluid power systems.
In apparatus for measuring the rate of fluid flow it has been proposed to measure the proportional rotational speed of a bladed or turbine-type rotor arranged in the path of the fluid. In the context of locating faults in fluid power systems, it is desirable to determine not only the fluid flow rate, but also the flow direction.
In the context of locating faults in fluid power systems, it is desirable to determine not only the fluid flow rate; but also the flow direction.
In one proposal during rotation of the rotor there is repeatedly presented to a magnetically permeable core of a fixed electromagnet magnetically permeable elements whereby to produce a cyclically varying reluctance. In this proposal the electromagnet is disposed in a blind radial bore which leaves a thin wall of a non-magnetic material between the poles of the magnetically permeable core and the path of the magnetically permeable elements. The thin wall is needed so that the variation in reluctance is noticeable but is unsuitable in fluid power systems where considerable pressure is experienced by the fitting. In another proposal the rotation of the rotor co-operates with a fixed element to constitute a cyclically variable capacitor. However, the fixed element is mounted in a saddle applied over an opening through the wall. Again such an arrangement is unsuitable in fluid power systems where considerable pressure is experienced. Neither of these proposals provides means for differentiating between opposite directions of rotation of the rotor.
Such means are however provided in another proposal using a rotor responsive to fluid flow and during its rotation repeatedly interrupting the path of radiation through the thickness of the wall of a conduit and across the flow of fluid. In this proposal high pressures are considered and the rotor is inserted in the conduit in a system to be tested and the radiation equipment is clamped to the conduit. In this proposal there is no need to bore into or through the wall of the conduit. However, the mounting of the radiation equipment would present difficulties because it would involve mounting on opposite sides of the conduit a transmitter and a receiver of radiation. In the majority of fluid power systems proprietary control valves are used for the purposes of achieving changes in the direction of fluid flow, changes in the rate of fluid flow and changes in fluid pressure. Such valves are designed usually to international standards with a plate having a plurality of ports therein for connection with pipes via well known standard fittings which expression embraces a wide variety of proprietary coupling devices manufactured to standard dimensions prescribed by national or international bodies in the field of fluid power engineering. The close pitching of the ports and therefore of the standard fittings by means of which the pipes are coupled to the valve results in minimal clearance between any two standard fittings which precludes the adaptation of a flow measuring device such as according to the last mentioned proposal.
In fluid power systems, the location of faults by a service engineer involves a need to determine information as to fluid flow at various points in the system. Such information is obtained from flow measuring apparatus either temporarily or permanently incorporated in the fluid power system. The temporary incorporation of flow metering apparatus in a fluid power system has the disadvantages that the fluid power circuit has to be broken and that the operation is time consuming. Hitherto, the permanent incorporation of fluid measuring apparatus in a fluid power system has suffered the disadvantage that, because each flow metering unit is a relatively expensive item, the cost of incorporating several such units usually exceeds the limit of practical economy.
Since a fluid power system almost invariably incorporates a number of standard fittings, the incorporation of a flow responsive element in such a fitting achieves a cost saving in that the fitting serves not only its usual purpose, but also serves as the body or housing of a flow metering unit.